UFS (Universal Flash Storage) is a storage standard which is developed for the purpose of achieving high throughput and low power consumption. In the UFS standard, a host is referred to as an initiator, and a memory device serving as an external storage device is referred to as a target. The target includes a nonvolatile memory such as a NAND-type flash memory.
In the UFS standard, when the target receives a write command from the initiator, the target prepares for the write command, and transmits Ready To Transfer UPIU designating the receivable data size and the like to the initiator. In response thereto, the initiator transmits Data Out UPIU serving as write data to the target. A packet based on UFS standard is referred to as UPIU.